However, you may be running a different desktop environment, so: What
desktop environment (KDE, GNOME, XFCE, ...) and what version of it are
you using, if any?

GNOME 2.32.1

Erk. Gnome hasn't shown problems previously, at least not with its
normal builtin clipboard manager (in gnome-settings-daemon). The way
xfce fixed their problems was by basing their new clipboard manager on
gnome's! However, I do not see any problem with gnome 2.30.2 on my
system. I don't know what gnome version Chong Yidong was testing with.

Just in case: Are you running anything else "clipboard related" on your
system? Say an alternative/extended clipboard history (may show up as a
little clipboard icon in your system tray).